What causes some transports to oscillate? [Archive] - Audio & Video Forums


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03-18-2013, 03:10 PM

Have you ever had a CD or CD/DVD player that will oscillate audibly, especially near the end of a disc? I have and I have contacted those in the know and the only thing I have been told is that the little magnetic disc clamp may be getting weak. I am not so sure.

My theory is that some discs have a center hole that is very slightly off center. Discs rotate more slowly as they near the end of play. If the disc is slightly off balance due to an off-center hole, they may wobble like a top slowing down which causes the disc clamp to wobble and contact the top plate of the transport producing a clicking or ticking noise - sometimes quite audibly.

But if the motor bearings were precise enough and rigid enough, should they not hold the entire process on center and prevent the wobble? My guess is that top-loading players either never wobble or do not do so audibly.

Also, I think that there are many more discs out there with off-center holes that we realize.

Would it not be possible for transport designers to take this into account and design transports that can deal with off-center holes more gracefully?

If my thinking is correct, why is this not more widely discussed and taken into consideration?

Thank you!



03-18-2013, 04:16 PM
Have you ever had a CD or CD/DVD player that will oscillate audibly, especially near the end of a disc? I've had quite a few since the early 80's and can't say I''ve ever run into this.

03-23-2013, 12:56 PM
Okay: I am going to answer my own thread. Careful observation has revealed that the transport itself is NOT oscillating. The spindle and disc clamp are perfectly concentric and plumb. What is happening is that the little upper part of the clamp that goes along for the ride as the CD is spinning does not always land concentrically after the CD loads. Thus, sometimes it will brush the sides of its mounting hole as it spins and produce extraneous noises. Unfortunately, said noises can get annoying at times. This could be considered a design flaw where the engineering was brilliant on paper, but not 100% in the field. Oh well . . .